But, it will be said, what can you mean by how things “really” seem and how they “seem” to seem? We come here upon an important fact about learning. When, in early infancy, we are learning to correlate sight and touch, we acquire the habit of reacting to a visual stimulus in a manner which is more “objective” than that in which a camera reacts. When we see a coin not directly in front of us, we judge it to be circular, although the camera would show it as oval, and a man would have to make it oval in a picture of a scene which contained it. We learn, therefore, to react to a visual shape in a manner corresponding to how it would appear if it were in the centre of the field of vision, provided we do not immediately focus upon it, which is what we naturally do when anything visible interests us. As a matter of fact, we are constantly looking in different directions, and, as a rule, only noticing what, at the moment, is in the centre of our field of vision. Thus our visual world consists rather of a synthesis of things viewed directly in succession than of things seen simultaneously while the centre of the field is kept fixed. This is one reason why the rules of perspective have to be learned, although a picture which ignores them makes an impression of being “wrong”. Another reason for the objectivity of the impressions we derive from sight is correlation with other senses, especially touch. Through this correlation we soon get to “know” that a man twenty yards away is “really” just as big as a man one yard away. When children are learning to draw, they find it very difficult to make distant objects sufficiently small, because they know they are not “really” small. We soon learn to judge the distance of a visual object, and to react to it according to the size that it would have if touched--or travelled over--in the case of very large objects such as mountains. Our sense of size is not derived from sight, but from such sources as touch and locomotion; our metrical judgments, when the stimulus is only visual, are a result of previous experience.